Interphase elastic properties

Functionalized Polyolefins and Aliphatic Polyamide Blends Interphase Interactions, Rheology, and High Elastic Properties of Melts... 

The mechanical properties of interfacial regions between fiber and matrix were also determined. The three-phase model was proposed, composed of fiber, interphase and matrix. If the properties of fiber, matrix and interphase layer are known, the mathematic procedure can be used to compute the elastic properties of the interphase. The mathematical model allows also to determine both the properties and the volume fraction of the interphase. 

Eor example, the effective elastic properties of silica nanopartides-reinforced polymer nanocomposites were predicted by means of various FEM-based computational models [70], induding an interphase layer around partides as a third constituent material in the prediction of the mechanical properties. Boutaleb et al. [30] studied the influence of structural characteristics on the overall behavior of silica spherical nanoparticles-polymer nanocomposites by means of analytical method and FEM. They assumed that the interphase between silica partide and polymer matrix presents a graded modulus, ranging from that of the silica to that of the polymer matrix, for example, a gradual transition from the properties of the silica to the properties of the polymer matrix (Figure 5.6). The change in elastic modulus in the interphase was described by a power law introducing a parameter linked to interfacial features. 

Naim [178] performed linear elastic stress analysis of residual stresses in unidirectional high-performance composites containing high-modulus fibers and an interphase region. Naim and Zoller [179] provided data for composites with thermoset and thermoplastic matrices, and showed by linear elastic stress analysis how the buildup of residual thermal stresses during fabrication is related to the disparate thermal expansion properties of the fibers and matrices. 

What are the elastic and inelastic properties ( y, X j, X, e, e, G,J, where i and = 1, 2, 3, within this interphase region, and how do they vary with radial distance from the fiber Also, are they isotropic and uniform along the length of the fiber How are the interphase properties related to the microstructure (Materials/Mechanics/Chemistry)... 

How do the elastic and inelastic properties and their distribution affect the interphase failure mechanisms/modes What are the typical failure modes How do we define interphase strength (the ultimate property which we use to define at what general loading state the fiber and matrix will separate parallel and perpendicular to the fiber direction) (Mechanics/Materials)... 

As predicted by CMC theory, some of the Table 4 properties will change significantly with fiber content and test direction. Nevertheless, for the selected fiber content and panel test conditions, qualitative trends can be observed in the as-fabricated CMC mechanical properties at room temperature. For example, regarding elastic modulus, variations between CMC systems can be correlated to the content of the high modulus CVI SiC matrix and to the existence of matrix porosity and/or an outside debonding interphase, both of which... 

A tentative model has been proposed to relate the interfacial shear strength at the fibre-matrix interface, measured by a fragmentation test on single fibre composites, to the level of adhesion between both materials. This last quantity has been estimated from the surface properties of both the fibre and the matrix and was defined as the sum of dispersive and acid-base interactions. This new model clearly indicates that the micromechanical properties of a composites are mainly determined by the level of physical interactions established at the fibre-matrix interface and, in particular, by electron acceptor-donor interactions. Moreover, to a first approximation, our model is able to explain the stress transfer phenomenon through interfacial layers, such as crystalline interphases in semi-crystalline matrices and interphases of reduced mobility in elastomeric matrices. An estimation of the elastic moduli of these interphases can also be proposed. Furthermore, recent work [21] has shown that the level of interfacial adhesion plays a major role on the final performances (tensile, transverse and compressive strengths and strains) of unidirectional carbon fibre-PEEK composites. 

The thermoplastic elastomers (TPE) are a new class of the polymeric materials, which combine the properties of the chemically cross-linked rubbers and easiness of processing and recycling of the thermoplastics [1-8], The characteristics of the TPE are phase micrononuniformity and specific domain morphology. Their properties are intermediate and are in the range between those, which characterize the polymers, which produce the rigid and elastic phase. These properties of TPE, regardless of its type and structure, are a function of its type, structure and content of both phases, nature and value of interphase actions and manner the phases are linked in the system. 

Structural properties can be investigated by small-angle neutron scattering (SANS) [3-5] or by quasi-elastic light scattering (QELS) [6-8]. Interphasal properties can be studied by dielectric spectroscopy and electrical conductivity mea-... 

One of the reasons for deviation of theoretical equations, connecting elasticity modulus with filler amount from the experimental data, is the formation of surface layers at the poljmier-filler interface (interphase layers). The properties of these layers are different than in bulk. It is very important to estimate the contribution of the interphase to the viscoelastic properties of composites. 

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